This blog is to provide a forum for students enrolled in Systems Management Course at IIIT-Delhi to have a meaningful discussion related to the course.

Tuesday, November 9, 2010

Comparison of Different Wireless Interface - 802.11 a/b/g/n

IEEE 802.11 is a set of standards for carrying out WLAN communication. Simply put, IEEE 802.11 specifies the way and means by which we can communicate on wireless networks. These usually operate at frequency bands of 2.4, 3.6 and 5.0 GHz. these standards are created and maintained by the IEEE LAN/MAN Standards Committee.

The table given below compares the standards:

802.11 Protocol

Freq. (GHz)

Bandwidth (MHz)

Data rate per stream (Mbit/s)

Allowable MIMO streams

Approximate indoor range (m)

Approximate Outdoor range (m)

1997

2.4

20

1, 2

1

20

100

a

5 / 3.7

20

6 - 54

1

35/--

120 / 16,000

b

2.4

20

5.5 - 11

1

38

140

g

2.4

20

6 - 54

1

38

140

n

2.4 / 5

20 / 40

7.2 - 72.2 / 15 - 150

4

70

250

Without considering the 3.7 GHz 802.11a band (the use of which is highly restricted by the Federal Communications Commission), we can see that 802.11n is the clear winner in terms of both range and speed. Also, 802.11n has a 5 GHz version, which takes care of the microwave interference problem. However, because of its high cost and low availability (in India), we generally use 802.11g as an alternative.

The microwave problem: Since 802.11b and g both operate in the 2.4 GHz band, they may experience interference whenever devices using the same frequency are operated near them. To describe it simply, this frequency band is like a one-lane road, and can only allow one-way traffic. So, when we operate, say, a microwave in the vicinity, we have to allow the "data" being transmitted by the microwave to transmit before our own wireless connection can operate. The microwave problem can reduce speed by 70 - 80%.

It was a pleasure to do our project, as it helped explain the differences between the interfaces, and which would be most suitable for different conditions. We thoroughly enjoyed doing the project, and would like to thank Dr. Amarjeet Singh for providing us with this opportunity.